I have a Pedersoli double in 45-70 and was thinking of rechambering to 45-120. how much of a gain in performance should I expect.
Thanks Dave

Dave,
i just bought a 45/120 reamer, as i am building a double... the 120 is a nearly 60% larger case ... and the 120 is about 4.5% smaller than a 450 NE....

i am aiming for easy 45/70 top loads.. 405 at 2100

could you do 500gr at 2100? yep, and cheap brass and cheap dies, vs the 450 ne

jeffe

I rechambered a Ruger No 3 to 45-120 in about 1990, and the answer was "As much as you can stand to shoot". I don't think this will be the case with the Pedersoli.

I might mention one thing. A couple of weeks after this, my local gunsmith called and asked if he could borrow the reamer. A guy in a neighboring town had a 45/70 Pedersoli and wanted to rechamber. I loaned it to him, and two days later he called again. Turned out the Pedersoli had a smaller bore than most 45/70's, and the pilot wouldn't enter the bore. I ended up selling the reamer to the guy so he could grind down the pilot to fit. It took several thousands to make it go. This was obviously an early Pedersoli. I wondered if anyone else had seen this in one of these guns?

Would a Pedersoli double still shoot to POA after a conversion like this? I know doubles are regulated to the intended load. Would it just be a matter of load development and possibly sight changes?

Jeff thanks for the info. I will slug the bore
after what Art said. If it is ok I think I will do it. I already have dies and brass. I know some were done to 450 NE and still regulated ok.
Dave

I don't know about the Pedersoli but there was a case of a 45-70 not opening far enough to swallow the extra long cartrige. The rim hit the standing breech. You may want to do a quick check on that.

Thanks I'll check that also